Space rockets, or launch vehicles, employ a great number of multiple contact, cylindrical, electrical connectors. The most commonly used is the bayonet coupled connector. This connector employs a bayonet coupling ring, wherein three circumferentially spaced cam grooves inside the rotary coupling ring, on the plug half, engage three bayonet pins secured to or projecting from the circumference of the receptacle to mechanically lock the plug half to the receptacle. While this provides very rapid engagement and disengagement of the plug relative to the receptacle, the ends of the cam grooves must necessarily include detents to prevent the bayonet pins from backing down the ramps defined by the cam grooves, and the coupling ring requires a spring to bias and hold the bayonet pins within the detents. The spring also accommodates the manufacturing tolerances in both the plug and receptacle halves, thus the plug shell or body is held in the receptacle of tubular form by a spring rather than being firmly locked to the receptacle and prevented from axial and transverse movement.
Recent qualification testing of devices employing the bayonet coupled connectors caused electrical failures of the connectors. The devices were the electro-explosive separation nuts used on the Titan III launch vehicle at the stage 0 to 1, 1 to 2 and 2 to 3 separation interfaces. The qualification tests included subjecting ten separation units including the mating electrical connector plugs to extreme mechanical shock and random vibration environments. After completion of the environmental tests it was found that several of the electrical pin male contacts in the connectors were broken and there was severe damage to the plug coupling ring and the receptacle bayonet pins.
Failure analysis of the connectors concluded that the broken electrical pins, and the damage, were caused by the relative motion that occurred between the plug shell and the receptacle during the application of the shock and random vibration environments. It was further determined that the spring member would have to be removed from the coupling ring design and that the plug body would have to be rigidly connected to the receptacle in order for the connectors to survive the extreme environments. A new coupling ring has been designed and is being tested. The new coupling ring is replaceable onto the existing plug shells and is intermateable with the existing receptacles.
There are approximately 500 existing wired and potted electrical connector plugs on existing Titan IIIC and IIID launch vehicles that will have to have the new coupling ring installed; and, therefore, the existing old coupling rings removed. The plugs are accessible by extending the plugs and approximately six inches of the attendant cable out of the vehicles through the holes used to route the cables to the separation nuts. With so many such plugs on cables that have already been installed and electrically tested, there is a need for the quick removal of the coupling rings without in any way comprising the mechanical and electrical integrity of the remaining plug shell and wiring.
With electrical connectors in this environment, care must be taken to prevent contamination of the connectors and excessive flexing of the harness during the cutting operation. The severance of the coupling ring results in the generation of small metal chips. As long as the chips remain outside the connector members, there is no problem. However, if one enters the tool receptacle during disconnection, it could be transferred to the next connector and, if this happens, serious problems could result in the launch vehicle operation. Excessive flexing of the wire during the cutting operation could lead to loose back shells or broken wires.
In attempting to sever the coupling rings, a small, variable speed drill motor was employed utilizing both thin metal cutting circular saws and abrasive cut off discs to sever the coupling ring lengthwise at two places 180.degree. circumferentially displaced. The use of such variable speed drill motors was unsatisfactory, since the severing process was too slow, too much heat was generated, an excessive amount of debris (chips and fillings) results, and it was necessary to create an elaborate fixturing to precisely control the contour of the cut.
In an alternate approach, a "nut buster" type device was employed to crack the coupling ring and to subsequently peel off the cracked coupling ring. A 10 inch plier type end cutter or nipper was reground to provide two cutting wedges with limited travel as opposed to the single cutter of a "nut buster". This was unsatisfactory because the compression force of the coupling ring was so great as to collapse the stainless steel receptacle shell onto the plug shell, thus damaging the plug shell. Also, even though the cutting wedges were positioned 180.degree. apart on the coupling rings, the rings could not always be peeled off because they tended to break into approximately 120.degree. and 240.degree. segments because of the three 120.degree. bayonet holes and cam grooves normal to such connectors.
Further, attempts to rupture or explode the coupling rings from within using mechanical leverage were made. However, this approach was abandoned because the hoop strength of the coupling ring is too great for the very thin wall levers which can be inserted between the coupling ring and the plug shell to achieve such rupture.
It is, therefore, a primary object of this invention to provide an improved cutter apparatus to sever circumferentially an electrical connector coupling ring in a safe and expeditious manner without affecting the mechanical and electrical quality integrity of the remaining plug shell and wiring.
It is a further object of the invention to provide an improved cutter apparatus for severing circumferentially a tubular member such as an electrical connector coupling ring which can be positioned at the proper axial position with respect to a plurality of spindle mounted cutting wheels surrounding the ring to be severed.
It is a further object of the present invention to provide an improved cutter apparatus for severing an electrical connector coupling ring or the like circumferentially in which a mandrel for attachment of the ring is projectable axially from the area of cutting to facilitate attachment and removal of the coupling ring thereto.
It is a further object of this invention to provide an improved cutter apparatus for severing an electrical connector coupling ring which does not exert undue forces on the cable, either tensile, twisting or repeated flexing at the connector and which does not damage or deteriorate the back shell, plug shell, insert or circuit contacts of the connector.